NDLI: Enhanced Groove Geometry for Herringbone Grooved Journal Bearings

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Schiffmann, J.
Copyright Year	2013
Abstract	Although gas lubricated Herringbone Grooved Journal Bearings (HGJB) are known for high rotordynamic stability thresholds, small clearance to diameter ratios are required for stable rotor operation. Tight clearances not only increase bearing losses but also yield challenging manufacturing and assembly tolerances, which ultimately translate into cost. Traditionally, the grooves of HGJB are of helical nature with constant cross-section and pitch. The current paper aims at increasing the clearance to diameter ratio and the stability threshold of grooved bearings by introducing enhanced groove geometries. The axial evolution of groove width, depth and local pitch are described by individual 3rd order polynomials with four interpolation points. The expression for the smooth pressure distribution resulting from the narrow groove theory is modified to enable the calculation of bearing properties with modified groove patterns. The reduced order bearing model is coupled to a linear rigid body rotordynamic model for predicting the whirl speed map and the corresponding stability. By introducing a critical mass parameter as a measure for stability, a criterion for the instability onset is proposed. The optimum groove geometry is found by coupling the gas bearing supported rotor model with a multi-objective optimizer. By maximizing both the clearance to diameter ratio and the rotordynamic stability it is shown that with optimal groove geometry, which deviates from helicoids with constant pitch and cross-section, the critical mass parameter can be improved by more than one order of magnitude compared to traditional HGJB geometries. The clearance to diameter ratio can be increased by up to 80% while keeping the same stability margin, thus reducing both losses and manufacturing constraints. The optimum groove pattern distributions (width ratio, angle and depth) are summarized for a variety of L/D ratios and for different compressibility numbers in a first attempt to set up general design guidelines for enhanced gas lubricated HGJB.
Sponsorship	International Gas Turbine Institute
File Format	PDF
ISBN	9780791855270
DOI	10.1115/GT2013-95464
Volume Number	Volume 7B: Structures and Dynamics
Conference Proceedings	ASME Turbo Expo 2013: Turbine Technical Conference and Exposition
Language	English
Publisher Date	2013-06-03
Publisher Place	San Antonio, Texas, USA
Access Restriction	Subscribed
Subject Keyword	Whirls Stability Compressibility Bearings Rotors Clearances (engineering) Pressure Geometry Design Interpolation Gas bearings Polynomials Manufacturing Journal bearings
Content Type	Text
Resource Type	Article

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